1 ELEN 602 Lecture 20 More on Routing RIP, OSPF, BGP

2 Command Version Zero Address Family Identifier Zero IP Address Zero Metric RIP Message Format

3 Area Area Area R1 R2 R3 R4 R5 R6R7 R8 N1 N2 N3 N4 N5 N6 N7 To another AS Area R = router N = network OSPF Areas

4 OSPF Summary Runs on top of IP, protocol number 89 Neighbors are discovered through hello messages Adjacencies are established and link-state databases synchronized. Propagate LSAs through exchanges between adjacent routers. Compute Routing tables.

5 Version Type Packet Length Router ID Area ID Checksum Authentication Type Authentication OSPF Message Header

6 Network Mask Hello Interval Options Priority Dead Interval Designated Router Backup Designated Router Neighbor 1 Neighbor n... OSPF Hello Packet

7 Interface MTU Options Zero I M Database Description Sequence Number LSA Header MSMS OSPF Database Description packet

8 Link State Age Options Link State Type Link State ID Advertising Router Link State Sequence Number Link State Checksum Length LSA Header

9 AS1 AS2 AS3 R1 R2 R3 R4 iBGP eBGP Internal and External BGP

10 BGP Summary Connects AS Domains Uses AS numbers for routing. BGP peers use TCP port number 179 for message exchanges Once the AS routing database established, only updates are sent between BGP peers iBGP peers need a consistent view of connectivity BGP peers exchange path-vectors of AS for routes Different types of messages: open, update, notification, keepalive.

11 R R R R iBGP eBGP R R R R iBGP iBGP Mesh

12 Marker Length Type: OPEN Version My Autonomous System Hold Time BGP Identifier Optional parameters length Optional Parameters Figure 8.44